1. Field of the Invention
The present invention is related to a control device and a robot using the control device, and more particularly, is related to a facial expression control device and a robot head using the facial expression control device.
2. Description of Related Art
The technique of emulation robot head having a humanoid appearance is proposed by Hara and Kobayashi of Tokyo Institute of Technology. They used pneumatic actuators to control the artificial facial skin fabricated by the silicone rubber. The artificial facial skin is provided with softness and flexibility, and thus the facial skin can express six basic facial expressions (surprised, frightened, sad, angry, happy and disgust) by pulling 19 control points disposed behind the facial skin. Wherein the selection of the control points are based on the facial expression coding system proposed by Ekman and 14 expression control units sufficient to compose 6 basic facial expressions are selected and used. And according to the definition, the expressions of human face can be composed from 44 groups of expression control units, i.e., the number of the expression control units determines the number of variation of expressions. Accordingly, many researchers regard this as a basis, and then the techniques related the robot head are published one after another, including the techniques of controlling facial skin variation by the methods of using memory alloy, motor, electroactive polymers (EVA) and the like, wherein the method of using motors to control facial skin for expression variation is the most commonly used. The main reason of using motors to control facial expressions is that motor has a faster response rate and uses electric power as the power source, and other assistant devices are not necessary (e.g., pneumatic compressors).
The well known companies who develop the related products of the emulation robot head include Kokoro of Japan, Hanson Robotic and Wow Wee of US and Xi An Superman of China. The robot heads of each of the above mentioned companies have different degree of freedom (DOF) (the expression variation) according to their different purpose. However, the expression variation mainly depends upon how many actuators have been used. In addition, the patents related to robot head include U.S. Pat. No. 7,113,848 and Japan Patent Publication No. 200235440. U.S. Pat. No. 7,113,848 discloses a humanoid face capable of facial expression including a plurality of actuators disposed in a casing, a linkage connected to the actuators and an outer skin connected to the linkage. Japan Patent Publication No. 200235440 discloses a humanoid face capable of facial expression including multiple flexible latching rings disposed at particular locations in an inner side of the skin, and the latching rings connected to the skin by a special connecting adhesive.
Review the currently known patents, references and products, it can be seen that, regardless of the way to achieve the facial expression, the robot head capable of facial expression generally has to use a large number of motors (e.g., 10 to 20 motors), pneumatic actuator, electric power driving memory alloy and the like to vary the controlling points of the facial skin to achieve different facial expressions. Each of the large number of actuators (motors, pneumatic actuators, electric power driving memory alloy) used in the conventional robot head operates in a way of capable to vary the position of one control point (a single degree of freedom). Thus in order that the robot head has a sufficient facial expressions (joyous, angry, sad, happy and the like), at least 12 motors is necessary to respectively drive different control point, resulting in manufacturing cost of the robot head remaining high and increase of difficulty of mechanism design and repair. The most important thing is the reliability of products may be decreased. And those reasons may be the main obstacle for the robot head capable of facial expressions to become a widespread product.